[HWYSTR455]

I've run all kinds of SCRs, heads, cams, distributors, ignition boxes, etc, and in my engines, I've always used .035-.040.

On my last iron head 400 which was about 9.95 SCR, it would det at anything above .035.

On spray, I never went over .035.

Bigger gaps also would give me a hotter operating temp. Between .045-.060, I could see as much as a 10-15 degree increase in water temps.

Wider gaps also wore caps & rotors faster, though never really saw plug life impacted, but I did change them fairly frequently.

Even now, with aluminum heads, and reasonable SCRs, I still run between .035-.040. Some plugs come pre-gapped, otherwise I would just run .035 on everything. I pretty much try to run plugs that allow for gap changes lately, some either can't be or have issues when trying to change the gap. (like some of the special tips ones).

Gaps can change timing requirements too, it was explained to me at one point, but foggy at the moment on the topic, mainly because at one point I just decided to stick with .035. Flame front I believe was the subject, and placement of the tip in the head.

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